Annular cutters or core drills as they are more popularly known are a different variation of hole saw that are much more efficient at making holes because they cut faster with more accuracy, especially when the cutter breaks through the wood. These cutters use an annular groove instead of a twisted groove. The annular cutter cuts the hole smoothly leaving a solid core at the center and is quite adept on wood, ferrous and non-ferrous metals as well as laminates and other man made materials. The reason they are more often called core drills is the fact that they cut along the edge of the hole leaving a perfect core to fall out when the cutting is done.
The first core drills were invented and patented in the early 1970’s by Dough Hougen and later improved upon several times in the 1980’s. Before it’s invention the only way to cut a hole in different materials was to drill a pilot hole with a regular drill bit and then use a scroll saw to follow the circle and for very tough surfaces such as steel you would have had to drill many holes around the perimeter of the circle only leaving a small amount of material between each hole to cut through. The core drill simplified the process and became widely accepted.
Today you can see the handiwork that core drills offer on a daily basis every time you use a door. The door handle has a cylinder that contains the locking mechanism that is circular and the core drill is used to make the hole for it. To make the process even faster jigs and guides were created to place on the door at the appropriate place that guide the core drill accurately through the material of the door depending on what kind of material is being used the appropriate core drill will be chosen.